Scholar Rock's Apitegromab Shows Significant Motor Function Gains in SMA Patients in Phase 3 SAPPHIRE Trial

Scholar Rock's Apitegromab has demonstrated significant motor function improvements in SMA patients in the Phase 3 SAPPHIRE trial, with 30.4% of patients achieving a ≥3-point improvement on the HFMSE compared to 12.5% on placebo. The FDA has accepted the Biologics License Application under priority review with a target action date of September 22, 2025. The commercial launch in the U.S. is expected in 2025.

Scholar Rock (NASDAQ: SRRK), a late-stage biopharmaceutical company, has announced positive results from the pivotal Phase 3 SAPPHIRE trial, published in the peer-reviewed journal The Lancet Neurology. The trial evaluated the investigational muscle-targeted therapy apitegromab for improving motor function in patients with spinal muscular atrophy (SMA). The data showed statistically significant and clinically meaningful improvements in motor function for patients receiving apitegromab compared to placebo, despite all participants receiving ongoing survival motor neuron (SMN)-targeted treatment.

The primary endpoint of the trial was met, with a mean difference in change from baseline in the Hammersmith Functional Motor Scale Expanded (HFMSE) of 1.8 points (p=0.019) for all patients receiving apitegromab 10 mg/kg and 20 mg/kg compared to placebo. Specifically, 30.4% of patients receiving apitegromab had a ≥3-point improvement in HFMSE versus 12.5% on placebo at 52 weeks. Additionally, 19.6% of patients receiving apitegromab had a ≥4-point improvement in HFMSE compared to 6.3% on placebo.

The safety profile of apitegromab was consistent with that observed in previous trials, with no new safety findings reported. The drug was well-tolerated across all age groups. Scholar Rock has submitted a Biologics License Application (BLA) for apitegromab to the FDA, which has been accepted under priority review with a target action date of September 22, 2025. The commercial launch in the U.S. is expected in 2025, with a projected European launch in 2026.

Apitegromab is an investigational fully human monoclonal antibody that inhibits myostatin activation by selectively binding the pro- and latent forms of myostatin in the skeletal muscle. It is the first muscle-targeted treatment candidate in SMA to demonstrate clinical success in a pivotal phase 3 clinical trial. The FDA has granted Fast Track, Orphan Drug, and Rare Pediatric Disease designations to apitegromab, and the European Medicines Agency (EMA) has granted Priority Medicines (PRIME) and Orphan Medicinal Product designations.

SMA is a rare, severe, genetic neuromuscular disease that affects an estimated 30,000 to 35,000 people in the United States and Europe. The disease is characterized by the irreversible loss of motor neurons, atrophy of the voluntary muscles of the limbs and trunk, and progressive muscle wasting that causes continuous motor function decline throughout life. While there has been progress in the development of therapeutics that address the loss of motor neurons, there continues to be a high unmet need for therapies that directly address the progressive muscle weakness that leads to loss of motor function in SMA.

Scholar Rock is focused on developing and commercializing apitegromab for children and adults with SMA and other severe and debilitating neuromuscular diseases. The company's proprietary platform has developed novel monoclonal antibodies to modulate protein growth factors with extraordinary selectivity. By harnessing cutting-edge science in disease spaces that are historically under-addressed through traditional therapies, Scholar Rock works to create new possibilities for patients.

References:
[1] https://www.marketscreener.com/news/pivotal-sapphire-trial-data-published-in-the-lancet-neurology-apitegromab-demonstrated-significant-ce7c51d9d88cf526